title: Mining the cinnabaramide biosynthetic pathway to generate novel proteasome inhibitors.
abstract: The cinnabaramides and salinosporamides are mixed PKS/NRPS natural products isolated from a terrestrial streptomycete and a marine actinomycete, respectively. They interfere with the proteasome and thus potentially inhibit the growth of cancer cells. The compounds exhibit a γ-lactam-β-lactone bicyclic ring structure attached to a cyclohexenyl unit and a PKS side chain. As a first step towards improving anticancer activity and permitting genetic approaches to novel analogues, we have cloned and characterized the cinnabaramide biosynthetic genes from Streptomyces sp. JS360. In addition to the expected PKS and NRPS genes, the cluster encodes functionalities for the assembly of the hexyl side chain precursor. The corresponding enzymes exhibit relaxed substrate specificities towards a number of synthesized precursors, enabling production of novel chlorinated cinnabaramides. These were isolated and analyzed for activity, revealing that derivatives bearing a chlorine atom in the PKS side chain show higher inhibitory potentials towards the proteasome's proteolytic subunits (especially the trypsin and chymotrypsin units) and higher cytotoxicities towards human tumor cell lines than the parent cinnabaramide A. Although their activities towards the proteasome were weaker than that of salinosporamide A, the cinnabaramides were found to inhibit the growth of various fungi with greater potency.
authors.affiliation: Department of Microbial Natural Products (MINS), Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarland University, Campus C2.3, 66123 Saarbrücken, Germany.
authors.forename: Shwan
authors.initials: S
authors.lastname: Rachid
authors.forename: Liujie
authors.initials: L
authors.lastname: Huo
authors.forename: Jennifer
authors.initials: J
authors.lastname: Herrmann
authors.forename: Marc
authors.initials: M
authors.lastname: Stadler
authors.forename: Bärbel
authors.initials: B
authors.lastname: Köpcke
authors.forename: Jens
authors.initials: J
authors.lastname: Bitzer
authors.forename: Rolf
authors.initials: R
authors.lastname: Müller
mesh_terms: D053898:Biosynthetic Pathways; D045744:Cell Line, Tumor; D006801:Humans; D007783:Lactones / Q000378:metabolism* / Q000494:pharmacology; D005810:Multigene Family; D011480:Protease Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D061988:Proteasome Inhibitors; D011758:Pyrroles / Q000378:metabolism* / Q000494:pharmacology; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics
chemical_list: D007783:Lactones; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011758:Pyrroles; C475865:marizomib; D046988:Proteasome Endopeptidase Complex